Biological mediated synthesis of RGO-ZnO composites with enhanced photocatalytic and antibacterial activity

Sonochemical synthesis of bioinspired graphene oxide-zinc oxide hydrogel for antibacterial painting on biodegradable polylactide film

Graphene oxide nanosheet (GO) is a multifunctional platform for binding with nanoparticles and stacking with two dimensional substrates. In this study, GO nanosheets were sonochemically decorated with zinc oxide nanoparticles (ZnO) and self-assembled into a hydrogel of GO-ZnO nanocomposite. The GO-ZnO hydrogel structure is a bioinspired approach for preserving graphene-based nanosheets from van der Waals stacking. X-ray diffraction analysis (XRD) showed that the sonochemical synthesis led to the formation of ZnO crystals on GO platforms. High water content (97.2%) of GO-ZnO hydrogel provided good property of ultrasonic dispersibility in water. Ultraviolet-visible spectroscopic analysis (UV-vis) revealed that optical band gap energy of ZnO nanoparticles (∼3.2 eV) GO-ZnO nanosheets (∼2.83 eV). Agar well diffusion tests presented effective antibacterial activities of GO-ZnO hydrogel against gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus). Especially, GO-ZnO hydrogel was directly used for brush painting on biodegradable polylactide (PLA) thin films. Graphene-based nanosheets with large surface area are key to van der Waals stacking and adhesion of GO-ZnO coating to the PLA substrate. The GO-ZnO/PLA films were characterized using photography, light transmittance spectroscopy, coating stability, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopic mapping (EDS), antibacterial test and mechanical tensile measurement. Specifically, GO-ZnO coating on PLA substrate exhibited stability in aqueous food simulants for packaging application. GO-ZnO coating inhibited the infectious growth ofE. colibiofilm. GO-ZnO/PLA films had strong tensile strength and elastic modulus. As a result, the investigation of antibacterial GO-ZnO hydrogel and GO-ZnO coating on PLA film is fundamental for sustainable development of packaging and biomedical applications.

Photocatalytic antibacterial agents based on inorganic semiconductor nanomaterials: a review

Microbial contamination and antibiotic pollution have threatened public health and it is important to develop a rapid and safe sterilization strategy. Among various disinfection strategies, photocatalytic antibacterial methods have drawn increasing attention due to their efficient disinfection performances and environment-friendly properties. Although there are some reviews about bacterial disinfection, specific reviews on photocatalysis focused on inorganic semiconductor nanomaterials are rarely reported. Herein, we present a systematic summary of recent disinfection developments based on inorganic nanomaterials (including metal oxides, sulfides, phosphides, carbon materials, and corresponding heterostructures) over the past five years. Moreover, key factors and challenges for inorganic nanomaterial-based photocatalytic disinfection are outlined, which holds great potential for future photocatalytic antibacterial applications.

Development of an environmentally sustainable technique to minimize the sludge production in the textile effluent sector through an electrokinetic (EK) coupled with electrooxidation (EO) approach

This study presents an environmentally sustainable method for minimizing sludge production in the textile effluent sector through the combined application of electrokinetic (EK) and electrooxidation (EO) processes. AAS and XRF analyses reveal that utilizing acidic electrolytes in the EK method successfully eliminates heavy metals (Cu, Mn, Zn, and Cr) from sludge, demonstrating superior efficiency compared to alkaline conditions. In addition, the total removal efficiency of COD contents was calculated following the order of EK-3 (60%), EK-1 (51%) and EK-2 (34%). Notably, EK-3, leveraging pH gradient fluctuations induced by anolyte in the catholyte reservoir, outperforms other EK systems in removing COD from sludge. The EK process is complemented by the EO process, leading to further degradation of dye and other organic components through the electrochemical generation of hypochlorite (940 ppm). At an alkaline pH of 10.0, the color and COD removal were effectively achieved at 98 and 70% in EO treatment, compared to other mediums. In addition, GC-MS identified N-derivative residues at the end of the EO. This study demonstrates an integrated approach that effectively eliminates heavy metals and COD from textile sludge, combining EK with EO techniques.

Preparation and Properties of GO/ZnO/nHAp Composite Microsphere Bone Regeneration Material

The purpose of this study is to explore the possibility of using graphene-zinc oxide-hydroxyapatite (GO/ZnO/nHAp) composite microspheres as bone regeneration materials by making use of the complementary advantages of nanocomposites, so as to provide reference for the clinical application of preventing and solving bacterial infection after implantation of synthetic materials. Firstly, GO/ZnO composites and hydroxyapatite nanoparticles were synthesized using the hydrothermal method, and then GO/ZnO/nHAp composite microspheres were prepared via high-temperature sintering. The graphene-zinc oxide-calcium phosphate composite microspheres were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), energy dispersion spectroscopy (EDS), water contact angle measurement, degradation and pH determination, and differential thermal analysis (DiamondTG/DTA). The biocompatibility, osteogenic activity, and antibacterial activity of GO/ZnO/nHAp composite microspheres were further studied. The results of the cell experiment and antibacterial experiment showed that 0.5% and 1% GO-ZnO-nHAp composite microspheres not only had good biocompatibility and osteogenic ability but also inhibited Escherichia coli and Staphylococcus aureus by more than 45% and 70%. Therefore, GO/ZnO/nHAp composite microspheres have good physical and chemical properties and show good osteogenic induction and antibacterial activity, and this material has the possibility of being used as a bone regeneration material.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

Tumor tropic delivery of FU.FA@NSs using mesenchymal stem cells for synergistic chemo-photodynamic therapy of colorectal cancer

To overcome the limitations associated with the targeting abilities of nanotherapeutics and drug loading capacity of mesenchymal stem cells (MSCs), the present study relies on the combination of MSCs tumor tropism with the controlled release function of nano-based drug delivery platforms to achieve tumor-specific accumulation of chemotherapeutics with minimal off-target effects. 5-fluorouracil (5-FU)-containing ceria (CeNPs) coated calcium carbonate nanoparticles (CaNPs) were functionalized with folinic acid (FA) to develop drug-containing nanocomposites (Ca.FU.Ce.FA NCs). NCs were then conjugated with graphene oxide (GO) and decorated with silver nanoparticles (Ag°NPs) to form FU.FA@NS, a rationally designed drug delivery system with O₂ generation capacity that alleviates tumor hypoxia for improved photodynamic therapy. Engineering of MSCs with FU.FA@NSs provided successful loading and long-term retention of therapeutics on the surface membrane with minimal changes to the functional properties of MSCs. Co-culturing of FU.FA@NS.MSCs with CT26 cells upon UVA exposure revealed enhanced apoptosis in tumor cells through ROS-mediated mitochondrial pathway. FU.FA@NSs released from MSCs were effectively taken up by CT26 cells via a clathrin-mediated endocytosis pathway and distributed their drug depots in a pH, H₂O₂, and UVA-stimulated fashion. Therefore, the cell-based biomimetic drug delivery platform formulated in the current study could be considered a promising strategy for targeted chemo-photodynamic therapy of colorectal cancer.

Construction of SnO2/CuO/rGO nanocomposites for photocatalytic degradation of organic pollutants and antibacterial applications

Water contamination by reactive dyes is a serious concern for human health and the environment. In this study, we prepared high efficient SnO₂/CuO/rGO nanocomposites for reactive dye degradation. For structural analysis of SnO₂/CuO/rGO nanocomposites, XRD, UV-Vis DRS, SEM, TEM-EDAX, and XPS analysis were used to characterize the physicochemical properties of the material. The characterization results confirmed great crystallinity, purity, and optical characteristics features. For both Rhodamine B (RhB) and Reactive Red 120 (RR120) degradation processes, SnO₂/CuO/rGO nanocomposites were tested for their photocatalytic degradation performance. The SnO₂/CuO/rGO nanocomposites have expressed the degradation rate exposed to 99.6% of both RhB and RR120 dyes. The main reason behind the photocatalytic degradation was due to the formation of OH radical's generation by the composite materials. Moreover, the antibacterial properties of synthesized SnO₂/CuO/rGO nanocomposites were studied against E. coli, S. aureus, B. subtilis and P. aeroginosa and exhibited good antibacterial activity against the tested bacterial strains. Thus, the synthesized SnO₂/CuO/rGO nanocomposites are a promising photocatalyst and antibacterial agent. Furthermore, mechanisms behind the antibacterial effects will be ruled out in near future.

Concurrent fabrication of ZnO-ZnFe2O4 hybrid nanocomposite for enhancing photocatalytic degradation of organic pollutants and its bacterial inactivation

In this research, we looked at how heterostructure fabrication, phase ratio, and crystalline nature affect the photocatalytic activity of ZnO/ZnFe₂O₄ nanocomposite for the degradation of Rhodamine B (RhB) dye when exposed to sunlight irradiation. Magnetic ZnO/ZnFe₂O₄ hybrid nanocomposites were made using a co-precipitation technique. The synthesized hybrid nanocomposite were analyzed using a variety of characterization techniques to understand more about their chemical, crystallinity, and photoactive characteristics. Using UV-Visible spectra, the absorption and photocatalytic efficiency of photocatalysts were investigated. By using XPS and FTIR measurements, the surface composition and functionalization of the produced nanocomposite were observed. The synthesized ZnO/ZnFe₂O₄ nanocomposites exhibit irregular morphologies, and the average crystallite size is about 30 nm, by the findings of the transmission electron microscope. When exposed to solar light for 90 min, the prepared photocatalysts exceed ZnO nanoparticles in terms of photocatalytic performance by more than 45%. Pseudo-first-order kinetics governs the adsorption of RhB onto nanocomposite surfaces. Finally, the ZnO/ZnFe₂O₄ nanocomposites were employed for antibacterial treatments against the waterborne pathogens Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus). The outcomes demonstrated that the optimal disinfection efficiency against E. coli and S. aureus germs were 98.6 and 97.4%, respectively, associated with superior cycling durability. Therefore, this work offers a simple and rapid approach to the development of hybrid nanocomposites that could be used to create various photocatalytic and optical materials.

Biosynthesis, Characterization, and Augmented Anticancer Activity of ZrO2 Doped ZnO/rGO Nanocomposite

Fabrication of ZnO nanoparticles (NPs) via green process has received enormous attention for its application in biomedicine. Here, a simple and cost-effective green route is reported for the synthesis of ZrO₂-doped ZnO/reduced graphene oxide nanocomposites (ZnO/ZrO₂/rGO NCs) exploiting ginger rhizome extract. Our aim was to improve the anticancer performance of ZnO/ZrO₂/rGO NCs without toxicity to normal cells. The preparation of pure ZnO NPs, ZnO/ZrO₂ NCs, and ZnO/ZrO₂/rGO NCs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), photoluminescence (PL), and dynamic light scattering (DLS). XRD spectra of ZnO/ZrO₂/rGO NCs exhibited two distinct sets of diffraction peaks, ZnO wurtzite structure, and ZrO₂ phases (monoclinic + tetragonal). The SEM and TEM data show that ZrO₂-doped ZnO particles were uniformly distributed on rGO sheets with the excellent quality of lattice fringes without alterations. PL spectra intensity and particle size of ZnO decreased after ZrO₂-doping and rGO addition. DLS data demonstrated that green prepared samples show excellent colloidal stability in aqueous suspension. Biological results showed that ZnO/ZrO₂/rGO NCs display around 3.5-fold higher anticancer efficacy in human lung cancer (A549) and breast cancer (MCF7) cells than ZnO NPs. A mechanistic approach suggested that the anticancer response of ZnO/ZrO₂/rGO NCs was mediated via oxidative stress evident by the induction of the intracellular reactive oxygen species level and the reduction of the glutathione level. Moreover, green prepared nanostructures display good cytocompatibility in normal cell lines; human lung fibroblasts (IMR90) and breast epithelial (MCF10A) cells. However, the cytocompatibility of ZnO/ZrO₂/rGO NCs in normal cells was better than those of pure ZnO NPs and ZnO/ZrO₂ NCs. Augmented anticancer potential and improved cytocompatibility of ZnO/ZrO₂/rGO NCs was due to ginger extract mediated beneficial synergism between ZnO, ZrO₂, and rGO. This novel investigation emphasizes the significance of medicinal herb mediated ZnO-based NCs synthesis for biomedical research.

Nanoarchitecture of graphene nanosheets decorated with NiCr layered double hydroxide for sonophotocatalytic degradation of refractory antibiotics

Highly efficient and durable catalysts for wastewater treatment are urgently required to tackle critical environmental issues. In this regard, NiCr LDH (NC), NiCr LDH-GO (NC-GO), and NiCr LDH-rGO (NC-rGO) nanocomposites were synthesized. The results of XRD, EDX, and FTIR analyses not only explored the crystallographic and chemical structures of catalysts but also confirmed the successful synthesis. Further morphological, physical, chemical, and optical characteristics of the catalysts were evaluated more by SEM, HRTEM, BET, DRS, and XPS techniques. The as-synthesized catalysts were used for the efficient mineralization of rifadin under 50 W LED visible light irradiation and the ultrasonic power of 150 W. Amongst, 0.75 g L^-1 of NC-rGO demonstrated high sonophotocatalytic efficiency (88%) in natural pH (pH = 8) of 15 mg L^-1 of rifadin. The introduced system is also powerful for the decontamination of pharmaceutical-containing wastewater as well as other refractory antibiotics. Moreover, the radical trapping experiments demonstrated that the main reactive species involved in the degradation of rifadin are ^•OH, h⁺, and O₂^•-. The possible intermediates were thoroughly investigated using GCMS analysis. Also, NC-rGO demonstrated superior antibacterial activity in comparison with NC, NC-GO samples.

Photocatalytic degradation of tetracycline using hybrid Ag/Ag2S@BiOI nanowires: Degradation mechanism and toxicity evaluation

The wide use of antibiotics has caused their continual release and persistence in the eco-system, subsequently giving birth to antibiotic resistant bacterial species in the aquatic environment, thereby necessitating immediate and efficient remediation of the contaminated environment. In the present study, we synthesized Ag/Ag₂S@BiOI nanowires with an average diameter of ∼150 nm and length of 3-5 μm using a hydrothermal method and employed them as photocatalysts for photocatalytic degradation of tetracycline as a model antibiotic. The nanowire achieved nearly complete degradation of tetracycline (∼99%) within 60 min at the optimal condition of 100 mg/L TC concentration and pH 2. The degradation followed pseudo-first order kinetics, with a rate constant of 0.06228 min^{- 1}. Our toxicity tests showed that the nanowire has negligible toxicity towards PBMC cells, suggesting it as a promising photocatalyst.

Enhanced Bactericidal Action of rGO-ZnO Hybrids Prepared by the One-Pot Co-precipitation Approach

Metal-based antimicrobials have the potential to profile sustainable solutions to infection care and health. In this study, we report the synthesis of rGO-ZnO hybrid nanostructures by a simple co-precipitation approach with various mass ratios of GO, and their antimicrobial potential was assessed. The structural analysis confirms the presence of a hexagonal wurtzite structure with peak shifting in hybrid nanostructures and increases in crystallite size (11-24 nm). Raman spectra revealed GO doping in the D band (1350 cm-1) and G band (1590 cm-1). Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were performed to investigate the surface morphologies of the synthesized sediments, which showed a change in the morphology of ZnO from non-uniform spherical nanoparticles to a rod-like morphology of the prepared hybrid nanostructures. RAMAN spectra revealed that the retained functional groups on rGO planes were significant in anchoring ZnO to rGO. At lowest and maximum doses of ZnO, substantial bactericidal zones (p < 0.05) for S. aureus (1.55 and 1.95 mm) and E. coli (1.25 and 1.70 mm) were achieved accordingly. Additionally, the inhibition regions were 2.45-3.85 mm and 3.75-6.85 mm for S. aureus whereas (2.05-3.25 mm) and (2.95-3.90 mm) for E. coli at the lowest and maximum concentrations.

Ceria nanoparticles anchored on graphitic oxide sheets (CeO2-GOS) as an efficient catalyst for degradation of dyes and textile effluents

Herein, we report a Ceria-graphitic oxide sheets (CeO₂-GOS) nanocomposites photo catalyst synthesized by simple and green methods for the degradation of textile effluents and dyes. In the first step, green treated CeO₂ NPs were synthesized through a simple organic reduction method. Further, green synthesized CeO₂ NPs were anchored with GOS to produce CeO₂-GOS nanocomposites by a sol-gel method. The phase morphology and structure of CeO₂-GOS nanocomposites was systematically characterized through X-ray diffraction, Raman spectroscopy, zeta potential, Fourier transform infrared spectroscopy (FT-IR), High-Resolution Transmission Electron Microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS) analysis. Under visible light irradiation, the CeO₂-GOS nanocomposites photo catalyst exhibited 83%, 78%, and 70% degradation efficiencies for rhodamine B, methylene blue, and textile effluent, respectively. Due to the synergistic impact of GO, it act as an elastic conductive channel permitting improved charge transport, the fabricated CeO₂-GOS nanocomposites showed a significant retort to photo catalysis of rhodamine B, methylene blue, and textile effluent. CeO₂-GOS nanocomposites may yield unique insight into the synthesis of green nanocomposites and their application in environmental remediation due to their better photo catalytic activity.

Assembling Hollow Cactus-Like ZnO Nanorods with Dipole-Modified Graphene Nanosheets for Practical Room-Temperature Formaldehyde Sensing

Formaldehyde (HCHO) sensing plays a critical role for indoor environment monitoring in smart home systems. Inspired by the unique hierarchical structure of cactus, we have prepared a ZnO/ANS-rGO composite for room-temperature (RT) HCHO sensing, through assembling hollow cactus-like ZnO nanorods with 5-aminonaphthalene-1-sulfonic acid (ANS)-modified graphene nanosheets in a facile and template-free manner. Interestingly, it was found that the ZnO morphology could be simply tuned from flower clusters to hollow cactus-like nanostructures, along with the increase of the reaction time during the assembly process. The ZnO/ANS-rGO-based sensors exhibited superior RT HCHO-sensing performance with an ultrahigh response (68%, 5 ppm), good repeatability, long-term stability, and an outstanding practical limit of detection (LOD: 0.25 ppm) toward HCHO, which is the lowest practical LOD reported so far. Furthermore, for the first time, a 30 m³ simulation test cabinet was adapted to evaluate the practical gas-sensing performance in an indoor environment. As a result, an instantaneous response of 5% to 0.4 ppm HCHO was successfully achieved in the simulation test. The corresponding sensing mechanism was interpreted from two aspects including high charge transport capability of ANS-rGO and the distinct gas adsorbability derived from nanostructures, respectively. The combination of a biomimetic hierarchical structure and supramolecular assembly provides a promising strategy to design HCHO-sensing materials with high practicability.

Enhanced Anticancer Performance of Eco-Friendly-Prepared Mo-ZnO/RGO Nanocomposites: Role of Oxidative Stress and Apoptosis

ZnO nanoparticles (NPs) have attracted great attention in cancer therapy because of their novel and tailorable physicochemical features. Pure ZnO NPs, molybdenum (Mo)-doped ZnO NPs, and Mo-ZnO/reduced graphene oxide nanocomposites (Mo-ZnO/RGO NCs) were prepared using a facile, inexpensive, and eco-friendly approach using date palm (Phoenix dactylifera L.) fruit extract. Anticancer efficacy of green synthesized NPs/NCs was examined in two different cancer cells. The potential mechanism of the anticancer activity of green synthesized NPs/NCs was explored through oxidative stress and apoptosis. The syntheses of pure ZnO NPs, Mo-ZnO NPs, and Mo-ZnO/RGO NCs were confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and photoluminescence (PL). Dynamic light scattering (DLS) study indicated the excellent colloidal stability of green prepared samples. Mo-ZnO/RGO NCs exhibited threefold higher anticancer activity in human colon (HCT116) and breast (MCF7) cancer cells as compared to pure ZnO NPs. The anticancer activity of Mo-ZnO/RGO NCs was mediated through reactive oxygen species, p53, and the caspase-3 pathway. Moreover, cytocompatibility of Mo-ZnO/RGO NCs in human normal colon epithelial (NCM460) and normal breast epithelial cells (MCF10A) was much better than those of pure ZnO NPs. Altogether, green stabilized Mo-ZnO/RGO NCs exhibited enhanced anticancer performance and improved cytocompatibility because of green mediated good synergism between ZnO, Mo, and RGO. This study suggested the high nutritional value fruit-based facile preparation of ZnO-based nanocomposites for cancer therapy.

Promising Graphene-Based Nanomaterials and Their Biomedical Applications and Potential Risks: A Comprehensive Review

Graphene-based nanomaterials (GBNs) have been the subject of research focus in the scientific community because of their excellent physical, chemical, electrical, mechanical, thermal, and optical properties. Several studies have been conducted on GBNs, and they have provided a detailed review and summary of various applications. However, comprehensive comments on biomedical applications and potential risks and strategies to reduce toxicity are limited. In this review, we systematically summarized the following aspects of GBNs in order to fill the gaps: (1) the history, synthesis methods, structural characteristics, and surface modification; (2) the latest advances in biomedical applications (including drug/gene delivery, biosensors, bioimaging, tissue engineering, phototherapy, and antibacterial activity); and (3) biocompatibility, potential risks (toxicity in vivo/vitro and effects on human health and the environment), and strategies to reduce toxicity. Moreover, we have analyzed the challenges to be overcome in order to enhance application of GBNs in the biomedical field.

Progress on photocatalytic semiconductor hybrids for bacterial inactivation

Due to its use of green and renewable energy and negligible bacterial resistance, photocatalytic bacterial inactivation is to be considered a promising sterilization process. Herein, we explore the relevant mechanisms of the photoinduced process on the active sites of semiconductors with an emphasis on the active sites of semiconductors, the photoexcited electron transfer, ROS-induced toxicity and interactions between semiconductors and bacteria. Pristine semiconductors such as metal oxides (TiO₂ and ZnO) have been widely reported; however, they suffer some drawbacks such as narrow optical response and high photogenerated carrier recombination. Herein, some typical modification strategies will be discussed including noble metal doping, ion doping, hybrid heterojunctions and dye sensitization. Besides, the biosafety and biocompatibility issues of semiconductor materials are also considered for the evaluation of their potential for further biomedical applications. Furthermore, 2D materials have become promising candidates in recent years due to their wide optical response to NIR light, superior antibacterial activity and favorable biocompatibility. Besides, the current research limitations and challenges are illustrated to introduce the appealing directions and design considerations for the future development of photocatalytic semiconductors for antibacterial applications.

Lactobacillus amylovorus derived lipase-mediated silver derivatization over poly(ε-caprolactone) towards antimicrobial coatings

Owing to the probiotic origin, lipases-derived from the Lactobacilli sp. are considered to be promising biomaterials for in vivo applications. On a different note, poly(ε-caprolactone) (PCL)-an FDA-approved polymer for implantable applications-lacks inherent antimicrobial property, because of which suitable modifications are required to render it with bactericidal activity. Here, we employ Lactobacillus amylovorous derived lipase to surface derivatize the PCL films with silver that is a highly efficient inorganic broad-spectrum antimicrobial substance. Two different surface functionalization strategies have been employed over the alkaline hydrolyzed PCL films towards this purpose: In the first strategy, lipase-capped silver nanoparticles (Ag NPs) have been synthesized in a first step, which have been covalently immobilized over the activated carboxylic groups on the PCL film surface in a subsequent step. In the second strategy, the lipase was covalently immobilized over the activated carboxylic groups of the PCL film surface in the first step, over which silver was deposited in the second step using the dip-coating method. While the characterization study using X-ray photoelectron spectroscopy (XPS) has revealed the successful derivatization of silver over the PCL film, the surface characterization using field-emission scanning electron microscopy (FE-SEM) study has shown a distinct morphological change with higher silver loading in both strategies. The antimicrobial studies employing E. coli have revealed 100 % inhibition in the bacterial growth in 4-6 h with the Ag NPs-immobilized PCL films as opposed to >8 h with those prepared through the dip-coating method. Additionally, the cytotoxicity assay using mouse fibroblast cells has shown that the PCL films immobilized with lipase-capped Ag NPs exhibit high cell compatibility, similar to that of pristine PCL film, and thereby making it suitable for in vivo applications.

Ce2O3/BiVO4 Embedded in rGO as Photocatalyst for the Degradation of Methyl Orange under Visible Light Irradiation

A p–n heterojunction semiconductor structure composed of Ce3O4 and BiVO4 has been synthesized and then incorporated into reduced graphene oxide (rGO) by the hydrothermal method. The ternary composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), and UV–vis spectroscopy. The efficiency of the composites as photocatalysts was determined by studying the oxidative degradation of methyl orange in aqueous solution under visible light irradiation. The effect of parameters such as pH, catalyst loading, and concentration of the dye solution was examined in order to determine their influence on the photocatalytic activity of the composites. The composite incorporated into reduced graphene oxide presented the highest percentage (above 90%) in 2 h time, attributed to the effect of the increased surface area. The process of the enhanced photocatalytic activity has been discussed based on the energy band positions of the nanoparticles within the composite.